Magnetically controlled friction clutch



1951 J. G. OETZEL MAGNETICALLY CONTROLLED FRICTION CLUTCH 3 Sheets-Sheet1 Filed Oct. 29, 1948 john rHu G eorg e;

Dec. 18, 195] J. G. OETZEL.

MAGNETICALLY CONTROLLED FRICTION CLUTCH 5 Sheets-Sheet 2 Filed Oct. 29,1948 ill NvsN-To cl hvx 660% 2 Dec. 18, 1951 J. G. OETZEL 2,578,716

MAGNETICALLY CONTROLLED FRICTION CLUTCH Filed Oct. 29, 1948 3Sheets-Sheet 5 39 a a J O Patented Dec. 18, 1951 f-MAGNETICALLYCONTROLLED FRICTION CLUTCH John George Oetzel, Belolt, Wis., assignor toWarner Electric Brake & Clutch Company, a corporation of IllinoisApplication October 29, 1948, Serial No. 57,326

4 Claims.

This invention relates to friction clutches and more particularlytothose of the type in which the force for engaging the clutch is derivedfrom the rotation of the driving clutch element by exerting africtionless magnetic drag on a part which normally rotates with saiddriving element but is rotatable relative to the latter to cause theclutch engaging action.

One object is to provide a clutch actuator of the above character inwhich the magnetic drag s produced in a novel manner.

A further object is to produce the magnetic drag by means of an electricgenerator having a nonrotatable stator with selectively energizablewindings thereon and a short circuited rotor adapted to dissipate thegenerated heat without danger of deterioration in service use.

Another object is to energize the clutch by the combined action of twoelectromagnetic drag producing devices, one of which generates currentfor energizing the other.

A more detailed object is to produce one part of the controllablemagnetic drag by an electric generator having a permanent magnet fieldand to utilize the generator current to energize a secondary magneticdevice to exert an additional magnetic drag for actuating the mainclutch.

Other objects and advantages of the invention will become apparent fromthe following detailed description taken in connection with theaccompanying drawings, in which Figure 1 is a fragmentary longitudinaldiametricai cross section of a clutch embodying the novel features ofthe present invention.

Fig. 2 is a cross section taken along the line 2-2 of Fig. 1.

Fig. 3 is a fragmentary section taken along the are 3-3 of Fig. 2.

Fig. 4 is a cross section taken along the line 4-4 of Fig. 1.

Fig. 5 is a view similar to Fig. 1 showing a modification.

Fig. 6 is a fragmentary view taken along the line 6-6 of Fig. 5.

While the invention is susceptible of various modifications andalternative constructions, I have shown in the drawings and will hereindescribe in detail the preferred embodiment. It is to be understood,however, that I do not intend to limit the invention by such disclosurebut aim to cover all modifications and alternative constructions fallingwithin the spirit and scope of the invention as expressed in theappended claims.

The invention is shown on the drawings embodied in a so-called multipledisk friction clutch or coupling 6 for transmitting rotary power from adriving shaft ID to a driven shaft II. Herein the shafts are alined witheach other and journaled in suitable bearings including an antifrictionbearing I in the hub of a stationary housing 8.

The clutch 6 is engaged by pressing into axial engagement a plurality ofplates or disks I2, I3, I4 and I5 arranged coaxially and composed ofsuitable friction material. Herein, the disk I4 is formed with a hub issplined at I! onto the driving shaft IO and loosely spline connected atI8 to the disks I2 and I3, the disks I3 and I4 being urged apart by aplurality of annularly spaced compression springs I9. A nut I 4 screwedonto the shaft I0 forms a rigid backing for the terminal disk I4. Thedriven shaft I I is keyed at to the hub of a casing 2i into which thedisks I5 are loosely splined as indicated at 22.

Journaled on bearings 23 on the driving shaft I0 is the hub 24 of anactuating disk 26 connected to the hub by screws and disposed adjacentto but axially spaced from the terminal clutch disk I2. A thrust bearing21 is interposed between the hub 24 and a flange 28 on a sleeve carriedby the shaft I0 and backed by a shoulder 29 acting through the innerrace of the bearing 1. An antifriction backing is thus formed for theactuating disk 26 which may rotate with the driving shaft II] but isadapted to turn relative thereto in either direction away from a normalclutchreleased position.

Angular motion of the disk 26 relative to the driving shaft I0 isconverted into axial movement of the terminal clutch plate I3 tocompress the driving and driven clutch plates together to engage theclutch 6. To obtain a substantial mechanical advantage and minimizefriction, the motion is transmitted through a force augmentingconnection 30 including elongated circumferentially sloping cam surfaces3I constituting the bottoms of a plurality of grooves 32 formed in theface of the disk 26 and coacting with balls 33 that roll in grooves 34in the opposed face of the terminal clutch disk I3. Preferably, theballs are held angularly spaced by a cage 35 and the grooves 32 and 34are concentric with each other and the clutch axis. The cam surfaces 3|,which may thus extend substantially throughout a full revolution in thecase of a unidirectional clutch, rise gradually and circumferentiallyfrom low points 36 in which the respective ball are seated when the disk26 is turned relative to the driving shaft to a normal clutch-releasedposition. Whenever the actuating disk 26 is free, it is maintained inthis clutch-released position by the action of the springs ll actingbackwardly through the antiiriction cam connection.

Electrically energized and selectively controlled A means indicatedgenerally at 45 are provided for exerting a magnetic drag or torque onthe actuating disk 26 to hold the latter back and thus cause relativeturning between the disk and the driving shaft l and actuation of thecam mechanism to engage the clutch 6. In the form shown in Fig. 1, thismeans comprises a stationarily mounted wound stator 36 adapted to beenergized by direct current to produce a magnetic field which threads arotor 31 in which electric currents are generated to produce themagnetic drag for retarding the clutch actuating member 26.

In the present instance, both the rotor and stator are composed ofmagnetic material such as iron and comprise rings 39 and 40 of U-shapedcross section with the radially projecting legs interrupted atcircumferentially spaced points to form outwardly projecting rotor poles4| and inwardly projecting stator poles 42, the end faces of which areof substantially equal arcuate lengths and closely spaced so as toregister with each other when the parts are angularly disposed as shownin Fig. 4. A multiple turn winding 43 is secured within the stator rinbetween the poles 42* and a single turn winding 44 comprising a heavyring of copper or the like which encircles the rotor ring between thepoles 4|. The stator ring 40 is pressed into the stationary casing 8which is made of non-magnetic material. In a similar way, the rotor ringis secured to the nonmagnetic hub 24 so as to turn with the clutchactuating disk 26.

The winding 43 is adapted to be energized by direct current from asuitable external source by controlling the opening and closing of acircuit through the winding, the degree of such energization beinggoverned in any preferred manner. Upon such energization, magnetic fiuxthreads the stator and rotor cores around the windings 43 and 44 and therotor tend to assume a position relative to the stator of minimumreluctance of the magnetic circuits through the poles, the faces ofwhich are then alined as shown in Fig. 4. As a result of this tendency,a drag proportional to the energization of the stator is exerted on therotor.

Under thi drag, the disk 26 is held back and the clutch disk l3 turnsahead resulting in relative angular motion between the two disks causingthe balls 33 to roll up the cam inclines 3| separating the disks I3 and26 and forcing the disk I2 axially to compress the clutch plates intofrictional gripping engagement with a force determined by the magneticdrag torque multiplied by the mechanical advantage of the cam mechanism.The shafts l0 and i I are thus coupled frictionally to transmit acorresponding amount of power.

' When the drag device 45 is again disabled by interrupting the circuitthrough the winding 43, the disk 26 is freedand the springs l9, actingbackwardly through the ball cam mechanism, turn the disk reversely toreleased position. The clutch is thus released and the shafts ill and IIare uncoupled.

w 4 adapted to withstand substantial heating without danger oideterioration.

In the modification shown in Figs. 5 and 6, the current for energizing amagnetic drag-producing means such as the device is derived fromrotation of the driving element itself by an auxiliary device which alsoimposes. an additional drag. The auxiliary device is an electricgenerator 46 preferably having a field member or rotor 41 which turnswith the actuating disk 25 and is permanently magnetized to avoid thenecessity of using slip rings. For this purpose, the rotor may comprisea ring or magnetizable material such as so-called Alnico pressed .ontothe hub 24 and havingangularly spaced and outwardly projecting polepieces 48.

The generator stator 49 comprises alaminated magnetic ring havinginwardly projecting pole pieces 50 and pressed into the casing 8adjacent the drag device 45. Series connected windings 5| are oppositelywound around the adjacent pole pieces 56.

When the circuit through th windings is open, the generator remainsinefiectual and the rotor turns in unison with the driving shaft, the"actuating-disk 26 remains in clutch-released position where it is heldby the springs l9 acting back through the cam mechanism. Now when thecircuit is closed, the generator is rendered active to produce amagnetic drag on the rotor proportional to the magnitude of thealternating current permitted to fiow in the windings 5!. This currentis fed into and utilized to energize the short-circuited armature brake45 above described. To this end, one terminal of the winding 5| isconnected through a control switch 52 to a rectifier 53 whose outputterminals are connected to the winding 43 of the magnetic brake 45. Theother generator terminal is connected to the rectifier, in this instancethrough 3. normally closed switch 54 and a resistance element 55 such,for example, as an incandescent lamp bulb. Thus, whenever the switch 52is closed, the generator 46 will be rendered operative not only toproduce a primary magnetic drag on the actuating disk 26 of the clutch 6but also to generate current for'energizing the magnetic brake 45 andthereby produce a drag supplementing that of the generator. As a result,the total drag on the disk 26 is of substantial magnitude even thoughthe driving shaft I0 may be turning at relatively low speed.

For some applications, the magnetic brake 45 is mainly useful to effectthe initial engagement of the clutch 6 after which it may be disabledand the engagement of the clutch continued under the action of the dragproduced by the generator 46 alone. Such disabling of the device 45 maybe effected by a relay 56 which becomes energized effectually after ashort delay following the initial closure of the generator circuit.Herein, the relay is energized by the voltage 'drop across the loadresistance 55 and a second similar resistance 51 and, in view of thehigh value of these resistances when they are cold, remains deenergizeduntil the lamp filaments have become heated. Thus, the switch 54 of therelay remains closed and a switch 58 is held open for a. short intervalthereby maintaining the generator 46 connected through the rectifier tothe brake 45.

When, after heating of the lamp filaments, the relay current hasincreased sufilciently to move the relay armature, the switch 54 isopened and the switch 58 is closed. This disconnects the rectifier andthe brake winding 43 from the generator whose armature circuit remainsclosed through the lamp 55 and a second lamp 59. Thereafter, the clutch6 is maintained engaged under a force proportional to the drag producedby the generator 46 alone.

It will be apparent from the foregoing that the improved clutch actuatoris readily adaptshafts, a friction clutch coupling said shafts, a 3

member mounted on said driving shaft for angular displacement relativethereto about the shaft axis, said member being normally rotatable withsaid driving shaft, an actuating connection between said member and saidclutoh' operable upon turning of 'the member relative to said drivingshaft away from and back to a clutch released position to efl'ectengagement and to permit disengagement of the clutch, an electricgenerator having a nonrotatable stator and an armature rotatable withsaid member, a magnetic brake operable when energized to retard therotation of said member and having a nonrotatable element adapted to beenergized by said generator and a rotor rotatable with said member,means by which said generator may be activated to impose a magnetic dragon said member and energize said brake, and means automatically operableafter a time interval to disable said brake while maintaining saidgenerator effectual in continuing the drag on said member.

2. The combination of, driving and driven shafts, a clutch havingfrictionally engageable elements respectively rotatable with saidshafts, a member normally rotatable with said driving shaft and mountedfor rotation relative thereto, means actuated in response to rotation ofsaid member relative to said driving shaft to apply and release saidclutch, permanently magnetized poles on said member, a stationarilymounted wound stator coasting with said poles to form a generatoroperable to produce a magnetic drag on the member, a magnetic inductorrotatable with said member and driving shaft, and a nonrotatable magnetenergized by the current delivered by said generator and coacting withsaid inductor to impose a magnetic drag thereon supplementing the dragproduced by said generator.

3. The combination of, driving and driven shafts, a clutch havingfrictionally engageable elements respectively rotatable with saidshafts, a member normally rotatable with said driving shaft and mountedfor rotation relative thereto, means operable by movement of said memberaway from a normal clutch released position to apply said clutch, amagnetic brake adapted when energized to exert a retarding force on saidmember, said brake having coacting relatively rotatable elements withsurfaces spaced apart, and an electric generator for energizing saidbrake having a rotor rotatable with said member and a nonrotatablestator.

4. The combination of, driving and driven shafts, a friction clutchcoupling said shafts, a member normally rotatable with said drivingshaft and mounted thereon for angular displacement relative theretoabout the shaft axis, means actuated in response to angular displacementof said member relative to said shaft to engage said clutch, and amagnetic brake adapted when energized to exert force retarding therotation of said member, said brake comprising a stationarily mountedwound stator and a coacting magnetic armature rotatable with said memberhaving a single turn short-circuited coil thereon enclosing a magneticcircuit through said stator and armature.

JOHN GEORGE OETZEL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,974,390 Eason Sept. 18, 19342,061,787 Warner Nov. 24, 1936 2,091,270 Colman Aug- 1987 2,374,688 LaBrie May 1, 1945

